Pneumatic elevator



May 9, 1967 w. c. KILPATRICK, JR

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INVZ'NTOR ATTORNEYS Patented May 9, 1967 3,318,418 PNEUMATEC ELEVATOR William C. Kilpatrick, .lr., 796 Fail-oaks Drive, New (Iastle, ind. 47362 Filed Feb. 3, 1966, Ser. No. 524,754 6 Claims. (CL 187-17) This invention relates generally to pneumatic elevators and in particular to a pneumatic elevator system which is fail safe for any of a wide variety of malfunctions and which can be economically installed and maintained.

While pneumatic elevators are not unknown in the prior art, recent business and residential construction patterns have made their use far more practical than has been the case in the past. :Most shopping center construction includes many one and two story buildings and these, including basement facilities, can accommodate two-story or at most three-story elevator service. Installation of hydraulic or electrical elevators is quite expensive and the cost, where only two levels are to be traversed, for example, is almost prohibitive. An economically installed and operated, trouble-free pneumatic elevator system for low rise buildings has, therefore, become a product having a wide market and fulfilling a genuine need in certain types of commercial construction. Pneumatic elevator installations of the type referred to also find use in one or two-story dwellings accommodating aged, infirm, handicapped or convalescent residents.

It is an object of the present invention to provide a pneumatic elevator system in which the air pressure of the pneumatic system is used to provide an interlock assuring proper functioning of the system and proper manipulation of the elevator controls when the elevator car is in the upper portion of the hoistway.

A further object of the present invention is to provide a pneumatic elevator system in which the elevator car is automatically leveled and accurately positioned at the desired upper level in the hoistway.

A further object of the present invention is to provide a pneumatic elevator system having an automatic cushioning feature as the elevator car settles to its lowermost position in the hoistway.

A further object of the present invention is to provide a pneumatic elevator system having a novel, low-friction seal between the outer surface of the elevator car and the sidewalls of the hoistway.

These and other objects will become apparent as the description proceeds with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of an elevator installation embodying the present invention and showing portions broken away to illustrate the interior construction.

FIG. 2 is a side sectional view of the portion of the elevator installation located at the base of the car when the car is at the upper level.

FIG. 3 is a schematic view illustrating a portion of the pneumatic circuit for the door lock safety means.

FIG. 4 is an enlarged side sectional view illustrating the interaction of the upper level car-access door and the control elements located on the adjacent door jamb, a portion of the door being shown in open position in solid lines and in closed position by broken lines.

FIG. 5 is a top plan view of the structure shown in FIG. 4.

FIG. 6 is an enlarged, side sectional view of a portion of the car and hoistway illustrating the flexible, minimum friction seal between these two components.

FIG. 7 is a schematic view showing the inside surface of the lower level access door and illustrating the means for preventing opening of this door when the car is at the upper level and the hoistway is abnormally depressured as by power failure.

FIG. 8 is a schematic wiring diagram of the electrical components in the installation.

Referring initially to FIG. 1 there is shown at 10 a generally rectangular hoistway which extends between a lower level defined by the floor area 11 and an upper level defined by the floor area ;12. The hoistway is provided with a lower, car access door 13 and an upper, car access door 14 both of which swing on appropriate hinges.

Within the hoistway, and shown at the upper level in FIG. 1, is a car '16, access to which is obtained through the doors '13 or 14. The car is movable as a piston vertically within the hoistway in response to pneumatic pressure existing in the hoistway beneath the car. A flexible, minimum friction sealing means, indicated generally at 17 in FIG. 1 provides a seal between the car and the adjacent hoistway surfaces (the seal 17 being shown in detail in FIG. 6 and described infra). A means for pressuring the hoistway takes the form of the blower 18 having a drive motor 19 and a centrifugal blower wheel 21. The output of the blower wheel moves through the housing 20 and through a first port 23 and a second port 24 into the portion of the hoistway just below the floor surface 11. The second port 24 is provided with a hinged closure member 24a which permits unobstructed llow of air from the housing 21 into the hoistway but which blocks flow of air from the hoistway back into the housing. The first port 23 is located somewhat above the port 24 and permits flow of air both into the hoistway and from the hoistway through the housing and out through the blower intake.

The portion of the hoistway beneath the floor 11 is also provided with suitable bottom rests 27 and 28 which engage the lower surface of the car when it is at the lower level.

As may be seen in FIG. 1, a vertical air conduit 29 extends from the blower housing 20 upwardly adjacent the hoistway and terminates at an air lock housing 31 located adjacent the upper margin of the door frame for the upper access door 1 4. .The pneumatic circuit of which the conduit 29 forms a part is shown in the schematic illustration of FIG. 3. As will be evident from FIG. 3, the housing 31 also has connected to it an air conduit 32 (not visible in FIG. 1) which branches into conduits 33 and 34. The conduit 33- (FIG. 1) communicates with the interior of a pressure responsive con trol, indicated general-1y at 36 in FIG. 1 and shown in detail in FIG. 2. The conduit 34 extends to an identical pressure responsive control 37, located on the opposite side of the hoistway and shown in broken lines in FIG. 1. The pressure responsive controls 36- and 37 form part of a safety means for preventing lowering of the car in the hoistway when the upper access door 14 is opened as will subsequently be explained. .As may best be seen in FIG. 2, the pressure control 36 (pressure control 37 being identical) is composed of a housing 38, the interior of which is divided by a flexible diaphragm or movable wall 39. The conduit 33- supplies air under pressure to the chamber below the movable Wall 39 and; a pressure switch sensing element 41 also is exposed to the pressure in the portion of the chamber below the wall 39, the sensing element 41 serving the pressure switch 42 (FIG. 8) which closes upon a pressure drop in the chamber below the wall 39' and opens when the chamber is pressurized.

The diaphragm 39' has attached thereto a member 43 which extends from the housing and which is moved vertically as the diaphragm moves in response to changes in pressure in the chamber below it. Attached to the member 43 is bell-crank linkage, indicated generally at 44 in FIG. 2, which serves to reciprocate an abutment or pin 46 slidable within bearings 47 between a. position in which the abutment 46 is withdrawn or retracted 1 from the hoistway to a position in which it extends into the hoistway, this latter position being shown in FIG. 2. It will be noted that the member 43 and the bell-crank linkage 44 is weighted so that when the pressure in the chamber 'below the diaphragm 39 falls, the abutment'46 will, by gravity, be extended into the hoistway. The pressure control 3-7 (FIG. 1) operates an identical abutment which moves into and out of the hoistway simultaneously with the abutment 46.

Referring to FIGS. 1 and 2, the means for arresting and leveling the car at the upper level, that is, in proper orientation to the upper, car access door includes air vent ports taking the form of closely spaced apertures 51 in the hoistway wall just above the abutment 46. The apertures 51 are formed along at least one side face of the hoistway and are unmasked by the base of the car as it moves into proper position at the upper level. A pressure switch sensing element 52 (FIG. 2) also extends into one of the apertures 51 and serves to sense when the car has unmasked the adjacent apertures 51. The sensing element 52 serves the pressure switch 53 (FIG. 8) which closes on a pressure rise indicating that V the car has unmasked the ports 51 and has reached the upper level.

The interior construction of the control 31 and its actuation by the upper access door 14 will now be described with reference to FIGS. 4 and 5. As may best be seen in FIG. the housing 31 is partitioned to provide a chamber 56 which communicates with the air conduit 29 leading from the blower housing 20 of FIG. 1. An outlet from the chamber 56 is provided by an aperture obstructed 'by a hinged closure 57. The closure is urged into aperture-obstructing position by the pressure in the chamber 56 and is opened by a pin 58 carried by a hinged closure 59 which cooperates with an aperture vent ing the chamber 61, surrounding the chamber 56, to atmosphere as indicated in FIG. 4. The closure 59 is suitably biased outwardly to its-position of FIG. 4 and a stop bracket 62 limits the opening movement of the closure 59. The pin 58 extends through the closure and is adapted to be engaged by the tip of the adjustable abutment 63 carried by a bracket 64 mounted on the upper margin of the door 14. As may best be seen in FIG. 5 the air conduit 32, leading to the diaphragm chamber of the control 36 (FIG. 2) communicates with V the chamber 61. As will beevident from FIGS. 4 and 5 when the door 14 is closed, the pin 63, carried by the door 14, will engage and depress the pin 58 which, in

I turn, will force'the closure 57 open, this open position of the closure 57 being illustrated in FIG. 5. With the closure 57 open and the closure 5 9 closed, air will pass between the conduits 29 and 32 (through the chambers 56 and 61) as indicated schematically in FIG. 3. When the -door 14 is open, as shown in solid lines in FIG. 4,

' the pin 63 will be separated from the pin 5'8, permitting the closure 57 to seal the chamber 56 and venting the chamber 61, and consequently the duct 32 and the diaphragm chamber of the. control 36, to atmosphere. As shown in FIG. 4, the bracket 64 is also formed so as to actuate, when the door 14 is closed, a door limit switch of the double pole double throw type identified at 71. The switching contacts operated by the switch 71 are indicated at 71a and 71b in FIG. 8.

Mounted adjacent the housing 31, on the door frame above the door 14, is a solenoid lock 73 which has a depending plunger 73a. The plunger 73w (FIG. 5) projects into an accommodating opening 74 (FIG. 4) in the bracket 64 carried by the door, the plunger 73a 'being withdrawn from the aperture 74 in the doom bracket when the solenoid 73 is energized.v

-As may best'be seen in FIG. 7, a means is provided for preventing opening of the lower, car access door 13 when the car is at the upper level. Under such conditions the pivoted arm 76 supported by the bracket 77 assumes a position in which it blocks opening of the access door 13. A weight 77 mounted on the arm 76 assures that the arm will assume this blocking position when the car leaves the lower level. The position of the arm assumed when the car engages it, moving it out of blocking position, is illustrated in broken lines in FIG. 7.

Referring to FIG. 6, the seal between the car and the adjacent hoistway surfaces will now be described. In FIG. 6 the car floor is identified at 81 and the underlying support beam is identified at 82. Extending along the marginal, underside surface of the car floor is a support bracket 93 which is Z-shaped in cross section and supports, by means of the studs 84 and spacer tubes 86, a strip of somewhat resilient fabric 87 having a pile face 87a. The fabric has a width greater than the clearance space between the car and the hoistway surface 88 and the pile surface faces the hoistway. The strip of fabric, when mounted, assumes a generally U-shaped configuration and is secured at both ends of the spacer tubes 86, with a support plate 89 extending over the upper leg of the fabric to approximately inch distance from the adjacent hoistway surface 88. As will be evident from FIG. 6, the mounting for the fabric is such that it is placed in resilient engagement with the adjacent hoistway surfaces as the car moves. As illustrated in FIG. 6, the car is at the upper level and the apertures 51 are unmasked by the seal 17.

The schematic wiring diagram of the electrical components of the system will now be described with reference to FIG. 8. The line wires L1 and L2 have main switches 101 interposed therein and are connected to the primary of a step-down transformer indicated generally at 102. Connected across the line conduits L1 and L2 is the blower motor 19 and in series with the blower motor are warp switch heaters 103 and normally open switches MS1 and M82, the switches M51 and M82 being closed by energize.- tion of the relay coil MS to be subsequently mentioned with reference to the low voltage circuit. Wires 104 and 106 extend from the secondary coil of the transformer 102 and have fuses 107 interposed therein. The pressure switch 53, which closes on pressure rise, is interposed in the line 106 as is the normally open switch MS3 which is operated to closed position upon energization of the relay coil MS previously referred to. The pressure switch 53 senses the pressure at the apertures 51 (FIG. 2), its sensing element being identified at 52 in FIG. 2. Wire 107 is connected to wire 106 and provides a circuit for the door lock solenoid 73 (referred to previously with ref-- erence to FIG. 5), the circuit extending to the wire 104. A wire 108 connects wire 106 with a timer motor 109. The timer motor 109 serves to mechanically open the timer contacts 111 approximately ten seconds, or for any other suitable time period, after energization of the timer motor, the contacts 111 remaining closed while the timer motor is deenergized and for a time delay period, such as ten seconds, after the timer motor 109 is energized. Controlling the circuit between the timer motor 109 and the wire 104 is the upper access door limit switch 71b previously referred to with reference to FIG. 4. A further step-down voltage transformer 114 has its primary coil connected across the wires 104 and 106 by means of the wires 112 and 113. A wire 116 connects one side of the secondary of transformer 114 to a lower, access door limit switch 118 which is actuated to closed position when the lower door 13 is closed. From the opposite side of the switch 118 a Wire 1119 is connected to one side of the normally open switch identified as M54, operated to closed position upon energization of the relay coil MS. The opposite side of the switch M84 is connected to a wire 121 and two additional switches, parallel to the switch MS4, extend between the wires 119 and 121, these switches being the normally open call ascend switch 122 and the car ascend switch 123. The call ascend switch 122 is operated by a push button, identified at 122a in FIG. 1 which is accessible at the upper level. The car ascend switch is also actuated by a push button located within the elevator car. The wire 121 is connected by three separate paths 124, 126 and 127 to the relay coil MS. The path provided by the wire 124 includes a call descend switch 128, actuated by a push button 128a shown in FIG. 1. The path identified at 124 has further interposed therein a car descend switch 129 which is operated by a push button within the elevator car. The timer contact 111, previously referredto, completes this circuit branch to the relay coil MS. The path identified at 126 includes the upper door limit switch 71a which is closed when the upper, access door is opened, this switch having been previously referred to with regard to FIG. 4. The path 127 includes the pressure switch 42 which closes upon a pressure drop within the diaphragm chamber of the control 36 (FIG. 2) and worse sensing element is identified in FIG. 2 at 41. The circuit from the opposite side of the relay coil MS to the secondary coil of transformer 114 is completed by wire 131 which has interposed therein warp switch contacts 103a operated to open position upon a predetermined overload, evidenced by generated heat, in the heaters 183.

In the operation of the system certain basic characteristics will be evidenced, these being (1) the car rests at the lower level when not in use, (2) the blower 18 runs continuously when the car is ascending or when it is waiting at the upper level, and (3) the blower 18 must be deenergized for descent of the car. Assuming that the system is in a quiescent state with the car at the lower level and with the blower deenergized, the control transformers 102 and 114 will be energized assuming the main switches 1 are closed. Upon opening the lower, access door 13, the lower door limit switch 118 will be opened. When the door closes after entry into the car, the switch 118 will close and the blower 18 may be started by manually actuating the car ascend switch 123. This energizes the relay coil MS through the switch 118, switch 123,'switch 128, switch 129 and switch -111. Energization of relay coil MS closes its hold-in switch MS4 and similarly closes switches M81, M82, and MS3. Closure of switches MS1 and M82 energizes the blower motor 19. As the blower attains operating speed the pressure beneath the car is raised, air entering this space through the ports 23 and 24 of FIG. 1. The car moves upwardly and, unless the car descend switch 129 is actuated from within the car or unless the upper level call descend switch 128 is actuated, the car will continue to the upper level. As the car reaches to approximately two inches from the upper level position, the pressure switch 53 is actuated to closed position because of the unmasking of the particular aperture in which the sensing element 52 (FIG. 2) is located. Closure of pressure switch 53 energizes the locking solenoid 73 so as to withdraw the locking pin 73a from the upper access door 14 (FIG. 5) and thus unlocks the upper access door. The timer motor 109 is also energized upon closure of pressure switch 53. If the upper access door 14 is not opened within the time delay provided by the motor 109, the timer will run through its delay period and will open the switch 111 to automatically shut off the blower 18 permitting the car to return to the lower level.

However, assuming the upper door 14 is opened upon reaching the upper level, when the door is opened the upper access door limit switch 71a is closed and the pressure switch 42 is also closed because of the depressuring of the chamber below the diaphragm 49 in the control 36, such depressuring occurring because of the venting of the chamber 61 past the closure 59 (FIG. 4). These two switches, that is, pressure switch 42 and upper door limit switch 71a parallel the circuit through the timer switch 111 and function to assure that the blower 18 cannot be deenergized while the upper, access door 14 is open. The upper door limit switch 71b is opened upon opening of the upper, access door so that the timer motor 109 is immediately deenergized and spring returned to a start position in which its contacts 111 are closed.

The blower 18 continues to run while the car is at the upper level. After the occupant leaves the car at the upper level, the door recloses and the blower may be manually deenergized by actuating the call descend switch 128, thus deenergizing relay coil MS, or the energization of timer motor 109 upon closure of switch 71b (moved to closed position by closing of the upper access door 14) serves to deenergize the relay coil MS, and consequently the blower motor 19, through the opening of the timer switch 111. When the blower is deenergized, the locking solenoid 73 is also deenergized because of the opening of switch M83 and the locking pin 73a (FIG. 5) drops by gravity into the upper access door 14 preventing it from being reopened. The air in the hoistway then is vented through the port 23, the housing 20 and out through the blower intake. The consequent slow decrease in pressure permits the car to descend to the lower level and just prior to its settling upon the rests 27 and 28 the port 23 will be obstructed by the base of the car, trapping air beneath the car and cushioning its final motion, this final motion being rather gradual because of the relatively slow leaking of air from the very lowest portion of the hoistway.

When a user is at the upper level and wishes to descend, the car may be brought to the upper level by actuating the call ascend switch 122 (the actuating button being identified at 122a in FIG. 1). This energizes the relay coil MS, and consequently the blower motor 1 9, through the switches 128, 129 and 111. The pressure beneath the ear is then raised and the car ascends to the upper level. As the car reaches the upper level the solenoid lock 73 is energized withdrawing the pin 73a from the upper access door 14 and permitting it to be opened. Opening the upper access door for entry depressures the chamber 61 of the control 31 and consequently depressures the chamber beneath the diaphragm 39 in the chamber 36 permitting the abutments 46 to extend into the hoistway assuring that the car is mechanically blocked from descending until the abutments 46 are retracted. Opening of'the upper access door 14 also opens the switch 71b which deenergizes the timer motor 109 and, after a ten second time delay causes the timer contacts 111 to reclose. Closing of the upper door limit switch 71a further assures that the relay coil MS cannot be deenergized and that the blower motor, consequently, cannot be deenergized while the upper access door 14 is open. The car may be subsequently made to descend by actuating the car descent switch 129 or by permitting the timer motor to automatically deenergize the blower motor 19 a predetermined time interval after the upper access door is reclosed. With the blower deenergized the car descends as previously described.

The various electrical and mechanical components of the system described above serve the following functions. The pressure switch 42, responsive to the pressure under the diaphragm 39 of the control 36, serves to assure that the blower cannot be turned off with the upper, access door 14 open. A further function of this switch is to assure that the chamber below the diaphragm 39 is at a sufficient pressure to retract the abutments 46 and to thus compensate for any time delay which might occur in the supplying of pneumatic pressure to the control 36. The upper, access door limit switch 71a serves the same basic function as the pressure switch 42 but provides a safety backup to pressure switch 42. With the combination of the limit switch 71a and the pressure switch 42 it is possible to obtain an instantaneous interlock function when the upper, access door is opened and yet provide sufiicient time delay on the closing cycle for the pneumatic controls 36 to perform their function since the blower cannot be deenergized until the pressure switch 42 closes indicating the space below the diaphragm 39 has been depressured and the abutments 46 have been retracted.

The timer motor 109 and its associated contacts 111 provide automatic deenergization of the blower and consequent return of the car to the lower level when not in use. The time delay of the timer motor 109 is adjustable and, assuming that the occupant has left the car at the upper level and the access door 14 has automatically reclosed, since the timer motor 109 has been energized when the pressure switch 53 closes, the relay or motor starter coil MS will be deenergized after a predetermined time, such as ten seconds, after energization of the timer motor 109. If the upper door is reopened during this time interval, the timer 109 is deenergized and spring returned to its start position ready to recycle when the upper door is again closed.

The lower, access door limit switch 118 opens when the lower, access door 13 is opened thereby preventing the blower from being energized while the lower, access door is open.

Automatic leveling at the upper level is achieved by venting the hoistway through the venting apertures 51 which are unmasked or exposed by the seal member 17 carried by the car as the car reaches the upper level. The volume of air vented is determined by the pressure required to sustain the car at the correct, upper level elevation.

The blower runs continuously while the car is ascend-j ing and while it is retained at the upper level. The blower must be deenergized before the car can descend. The car seal, formed by a relatively dense fibrous material, presses lightly against the hoistway Wall surfaces and the fibers appear to present an efiective discharge coefficient of a magnitude such that the kinetic energy of the air in the hoistway under the car is transformed to pressure energy and, while the seal is quite flexible, allowing for large irregularities in the hoistway surfaces, the relatively low friction seal requires no lubrication and evidences little wear after prolonged use.

The air discharge slot or port 23 (FIG. 1) through the hoistway wall is covered by the car seal 17 during the last portion of travel downwardly of the car thereby trapping air in the hoistway under the car and causing a momentary pressure rise .which retards the downward velocity of the car and provides a cushioned stop on the rests 27 and 28. The amount of motion retardation is directly proportional to the downward velocity of the car and this results in a relatively constant landing velocity regardless of thespeed .of the car which is affected somewhat by the car load.

The safety interlock provided by the door-actuated control 31 and the control 36 provides protection in the event of power failure while the upper door 14 is open.- It will be understood that to provide various settling characteristics for the car the blower intake may be valved by, for example, a butterfly valve connected to a linkage arranged so that the car actuates the linkage to cause the desired obstruction to the reverse flow of air through the blower intake as the car reaches the proper level. It should also be understood that while a generally rectangular (in cross section) hoistway and car have been shown and described in detail herein, the hoistway'and the car accommodated in it might be fabricated circular in cross section and thereby permitting a revolving motion of the car as it moves between levels so as to permit entry and egress to the car from opposite sides'of the hoistway. If the car is overloaded at the upper level with the upper access door open (as would normally be the case during loading of the car), the car will sink slightly to-rest on the abutments 46 which will be extended because of the open condition of the upper door. Friction will prevent retraction of the abutments even though the upper door is reclosed and the car, therefore, cannot descend until the overload has been removed from the car and the upper door again closed.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as other modifications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being made to the appended claims.

The invention claimed is:

1. In a pneumatic elevator installation of the type wherein a car moves as a piston vertically within a hoist- Way in response to pneumatic pressure existing in the hoistway beneath the car between a lower level at which the car is properly positioned with respect to a lower caraccess door in the hoistway and an upper level at which the car is properly positioned with respect to an upper car-access door, means for arresting and leveling the car at the said upper car-access door comprising an air vent port for venting air from said hoistway, said port cooperating with said car so that as said car reaches proper position with relation to said upper car-access door said port is unmasked by the car in an amount sufficient to reduce the pressure in the hoistway space beneath the car to a value sufiicient to hold the car immobile at the upper level.

2. A pneumatic elevator arresting and leveling means as claimed in claim 1 wherein said port takes the form of a beit of closely spaced apertures extending transversely along at least one side face of said hoistway.

3. In a pneumatic elevator installation of the type wherein a car moves as a piston vertically within a hoistway in response to pneumatic pressure existing in the hoistway beneath the car between a lower level at which the car is properly positioned with respect to a lower car-access door in the hoistway and an upper level at which the car is properly positioned with respect to an upper car-access door, means for cushioning the final portion of the downward motion of said car as it moves from said upper level to said lower level comprising a first and second port in said hoistway for introducing air under pressure therein, said first port being positioned in said hoistway so as to be obstructed by said car as the car moves through said final portion of its downward motion and said second port being positioned in said hoistway below and not obstructed by said car when at said lower level, said second port having a check valve associated therewith to permit air flow through said second port into said hoistway but to prevent air fiow from the hoistway through the second port, whereby air under pressure may be introduced through both of said ports into said hoistway as said car ascends and may be vented from said hoistway through said first port as said car descends, the car being cushioned and slowed as it moves through said final portion of its downward motion by the air trapped beneath the car as said first port is obstructed.

4. In a pneumatic elevator installation of the type wherein an electrically operated air moving means forces air into a hoistway adjacent its base and an elevator car moves as a piston vertically within the hoistway in response to the pneumatic pressure existing in the hoistway beneath the car between a lower level at which the car is properly positioned with respect to a lower car-access door in the hoistway and an upper level at which the car is properly positioned with respect to an upper car-access door, safety means for mechanically blocking descent of the car from the upper level to the lower level when said upper access door is open and independently of the pressure in said hoistway, said safety means comprising an abutment extensible into said hoistway to block movement of the car, a pressure responsive control associated with said abutment and operable to permit said abutment to extend into the hoistway except when said control is from said hoistway to said control, and a valve interposed in said conduit and actuated by said upper access door to pass air from the hoistway to said control when said door is closed and to block air flow between the hoistway and the control and to vent to atmosphere the portion of said conduit between the valve and the control When said door is open, whereby said abutment is extended into the hoistway when said door is open independently of the pressure in said hoistway.

5. A pneumatic elevator safety means as claimed in claim 4 wherein said control includes a pressure chamber and a movable wall and linkage connecting said wall and said abutment operable to permit said abutment to extend by gravity when said chamber is vented to atmosphere and to retract said abutment from said hoistway when said chamber is pressurized.

6. A pneumatic elevator safety means as claimed in claim 4 wherein a pressure responsive switch responsive 10 to the pressure at said control and controlling energization of said air moving means is operable to prevent deenergization of the air moving means unless said control is supplied with air from said conduit and said abutment is therefore retracted from said hoistway.

References Cited by the Examiner UNITED STATES PATENTS 3/1960 Kristek 18717 1/1962 Fehlmann 187-17 EVON C. BLUNK, Primary Examiner.

HUGO O. SCHULZ, Examiner.

H. C. HORNSBY, Assistant Examiner. 

1. IN A PNEUMATIC ELEVATOR INSTALLATION OF THE TYPE WHEREIN A CAR MOVES AS A PISTON VERTICALLY WITHIN A HOISTWAY IN RESPONSE TO PNEUMATIC PRESSURE EXISTING IN THE HOISTWAY BENEATH THE CAR BETWEEN A LOWER LEVEL AT WHICH THE CAR IS PROPERLY POSITIONED WITH RESPECT TO A LOWER CARACCESS DOOR IN THE HOISTWAY AND AN UPPER LEVEL AT WHICH THE CAR IS PROPERLY POSITIONED WITH RESPECT TO AN UPPER CAR-ACCESS DOOR, MEANS FOR ARRESTING AND LEVELING THE CAR AT THE SAID UPPER CAR-ACCESS DOOR COMPRISING AN AIR VENT PORT FOR VENTING AIR FROM SAID HOISTWAY, SAID PORT COOPERATING WITH SAID CAR SO THAT AS SAID CAR REACHES PROPER POSITION WITH RELATION TO SAID UPPER CAR-ACCESS DOOR SAID PORT IS UNMASKED BY THE CAR IN AN AMOUNT SUFFICIENT TO REDUCE THE PRESSURE IN THE HOISTWAY SPACE BENEATH THE CAR TO A VALVE SUFFICIENT TO HOLD THE CAR IMMOBILE AT THE UPPER LEVEL. 